The need for relatively nonaromatic liquid hydrocarbons boiling in the range of about 300.degree. to 700.degree.F. (aviation turbine fuels, diesel fuels, and solvents, for example) continues to increase. These products usually, or at least often, contain relatively high percentages of olefins and monocyclic and polycyclic aromatics so that further hydrogenation is desirable to produce acceptable products. The presence of sulfur compounds in these products to be hydrogenated complicates the process of hydrogenation in that sulfur poisons many of the metal catalysts used for hydrogenation.
The hydrogenation of unsaturated hydrocarbons, particularly aromatic hydrocarbons, to corresponding saturated hydrocarbons using a platinum and/or palladium catalyst is disclosed in U.S. Pat. No. 3,637,484. The platinum and/or palladium is deposited selectively by cation exchange upon a silica-alumina cogel or copolymer which in turn is dispersed in a large pore alumina gel matrix. U.S. Pat. No. 3,674,838 discloses a process for selectively hydrogenating unsaturated hydrocarbons in the liquid phase utilizing a palladium-on-alumina catalyst. The catalyst is the product resulting from contacting alumina agglomerates of a specified surface area with steam, and after additional treatment, admixing the agglomerate with a palladium compound and subsequently calcining the resulting mixture. As noted briefly before, however, a primary disadvantage of using either the platinum or palladium catalysts is the ease with which these catalysts are poisoned with sulfur and nitrogen compounds and thereby rendered ineffective.
A primary object of this invention is to provide a catalyst and process for hydrogenating petroleum fractions containing aromatics, and olefins as well as sulfur and nitrogen compounds.